共查询到20条相似文献,搜索用时 171 毫秒
1.
2.
在激光技术研究、高速摄影、快电子学测量等领域中,高压大电流的纳秒脉冲信号源作为专用测试仪器是必不可少的。随着科研的不断深入,对不同类型的纳秒脉冲源要求越来越高,技术指标也越来越高。由于这类仪器同物理实验类型关联性强,量少,技术指标高,一般仪器生产厂商不开发生产。在固体器件(如雪崩晶体管)出现前,这类信号源是通过闸流管、火花隙、水银开关等器件来实现,不但体积大,触发延迟和触发抖动大,可靠性差,而且需要高于输出脉冲幅度的高压直流供电电源。为对具有高压脉冲信号幅度高、前沿快、宽度大、触发同步性好、可靠性高、体积小等特点高性能快前沿高压脉冲信号源的需求, 相似文献
3.
4.
5.
6.
7.
大腔体静高压技术在现代工业和高压科学研究中具有基础性的重要意义,已被广泛应用于工业和科研领域,如超硬材料的合成、凝聚态物质在高温高压极端条件下的行为与物性研究等。经过逾半个世纪的不懈努力,以国产铰链式六面顶压机为代表的大腔体静高压技术与设备取得了长足的发展和丰硕的成果,改变了长期以来我国大腔体静高压技术落后于国外的局面。文章以四川大学高压科学与技术实验室为例,对我国大腔体静高压技术及装置从起步研制到世界领先的发展历程和技术特点进行了介绍。同时,基于典型大腔体静高压技术、装置及主要应用,展望了我国相关领域的发展前景。 相似文献
8.
用金刚石压砧高压X光衍射技术研究了Ⅱ-Ⅵ族化合物CdTe的室温状态方程和室温高压相变。实验的最高压力达39.2 GPa。实验中发现CdTe从(3.3±0.1)GPa开始从闪锌矿结构相相NaCl结构相转变,相变时体积收缩15.8%;从(10.3±0.2)GPa开始从NaCl相向β-Sn结构相转变,相变时无体积突变;在(12.2±0.2)GPa由β-Sn相向正交结构相转变,相变时也无体积突变。CdTe的压缩数据用最小二乘法以Bridgman状态方程和Murnaghan状态方程拟合,得到其零压时合相变压力时各个相的体弹模量及体弹模量的压力微商,并与其它的实验合理论结果进行比较。 相似文献
9.
10.
11.
《中国物理快报》2020,(8)
Pressure generation to a higher pressure range in a large-volume press(LVP) denotes our ability to explore more functional materials and deeper Earth's interior. Pressure generated by normal tungsten carbide(WC) anvils in a commercial way is mostly limited to 25 GPa in LVPs due to the limitation of their hardness and design of cell assemblies. We adopt three newly developed WC anvils for ultrahigh pressure generation in a Walker-type LVP with a maximum press load of 1000 ton. The hardest ZK01 F WC anvils exhibit the highest efficiency of pressure generation than ZK10 F and ZK20 F WC anvils, which is related to their performances of plastic deformations.Pressure up to 35 GPa at room temperature is achieved at a relatively low press load of 4.5 MN by adopting the hardest ZK01 F WC anvils with three tapering surfaces in conjunction with an optimized cell assembly, while pressure above 35 GPa at 1700 K is achieved at a higher press load of 7.5 MN. Temperature above 2000 K can be generated by our cell assemblies at pressure below 30 GPa. We adopt such high-pressure and high-temperature techniques to fabricate several high-quality and well-sintered polycrystalline minerals for practical use. The present development of high-pressure techniques expands the pressure and temperature ranges in Walker-type LVPs and has wide applications in physics, materials, chemistry, and Earth science. 相似文献
12.
In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press 下载免费PDF全文
Here, simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press (LVP) up to 15 GPa and 1400 K by an acoustic travel-time approach. Based on the recently reported P-tS and P-T-tP-tS equations for Al2O3 buffer rod, the cell pressures and temperatures in the chamber of LVP were in-situ determined, in comparison with those by conventional off-line (or fixed-points) pressure calibration method and direct thermocouple measurement, respectively. It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures, owing to the stress relaxation as accumulate in the LVP chamber. This acoustic travel-time method is verified to be a good way for precise determination of thermal (cell) pressures at high temperature conditions, and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P-T conditions, especially when the precious synchrotron x-ray/neutron diffraction beams are not available. 相似文献
13.
G. V. Boriskov A. I. Bykov N. I. Egorov M. I. Dolotenko V. N. Pavlov V. I. Timareva 《等离子体物理论文集》2011,51(4):339-348
Experiments on isentropic compression of a substance using a high magnetic field pressure are described. Their goal is building of a zero isotherm in a multi‐megabar pressures range. A method of the pressure and density determination of the compressed substance based on radiographic data obtained in the experiment is presented. The results of the experiments with solid (in initial state) protium and deuterium are presented. The densities that correspond to more than seventeen‐fold compression are reached. Obtained experimental points are compared with extrapolation of a curve that is built in the experiments using anvil cells and with the results of several ab‐initio calculations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
三维拉曼边带冷却后的铯原子样品装载于一个磁悬浮的大体积交叉光学偶极阱中, 继续加载一个小体积的光学偶极阱后, 实现了Dimple光学偶极阱对铯原子的高效装载. 对不同磁场下磁悬浮大体积光阱的有效装载势能进行理论分析与实验测量, 得出最优化的梯度磁场和均匀偏置磁场, 获得了基于磁悬浮大体积光阱的Dimple光学偶极阱的装载势能曲线, 实现了Dimple光学偶极阱对经拉曼边带冷却后俘获在磁悬浮的大体积光阱中的铯原子样品的有效装载. 比较了Dimple光学偶极阱分别从拉曼边带冷却、大体积的交叉光阱和消除反俘获势后的磁悬浮大体积光阱装载的结果, 将俘获在磁悬浮大体积光阱中的铯原子样品装载到Dimple光学偶极阱, 铯原子样品的密度提高了约15倍. 相似文献
15.
R. Boehler 《Hyperfine Interactions》2000,128(1-3):307-321
Very high temperatures (>2000 K) at megabar presures (∼100 GPa) can be achieved by classic shock compression experiments and
in laser-heated diamond cells, which have evolved to a formidable tool for accurately characterizing material properties at
controlled pressure and temperature conditions of the Earth's lower mantle and core. The diamond cell has great potential
for future development and broad application but due to the small sample dimensions there are strict experimental requirements
for obtaining reliable data, some of which are described in the present paper. Results for measuring melting temperatures
of iron at very high pressure, which constrain the temperature in the Earth's centre, are reviewed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Grabovskii E. V. Gribov A. N. Oleinik G. M. Tkachenko S. I. Shishlov A. O. 《Physics of Atomic Nuclei》2018,81(7):1093-1098
Physics of Atomic Nuclei - The output unit of the Angara-5-1 installation was upgraded in order to increase megabar pressure. Upgrading was carried out taking into account those fact that pressure... 相似文献
17.
V. V. Kechin 《JETP Letters》2002,76(7):436-439
It is shown that the isotherms of isoelectronic materials in the statistical model converge in the megabar pressure range. The convergence of isotherms is universal and depends neither on the crystallographic structure nor on the specific type of the intermolecular potential. It is pointed out that the majority of compounds and minerals which constitute the Earth’s mantle are isoelectronic with neon. The melting curves of isoelectronic materials are parallel to each other. The mutual arrangement of the melting curves depends on the number of atoms in the molecule. Computations of the shear moduli of materials at 1 Mbar show that the materials with small number of electrons per atom have the lowest shear modulus. These materials are preferable for using as pressure-transmitting media in the megabar pressure range. 相似文献
18.
The behavior of elastic moduli of substances is analyzed in the megabar pressure range. A new effect—inversion of the shear moduli and mechanical properties upon compression—is predicted for various classes of substances. The melting-curve data for different materials confirm the predicted phenomenon. The materials traditionally considered the softest, such as rare gas solids and molecular substances, may become the hardest in the megabar range. This should be taken into account in developing the experimental high-pressure technique. 相似文献
19.
R. F. Trunin G. V. Boriskov A. I. Bykov A. B. Medvedev G. V. Simakov A. N. Shuikin 《JETP Letters》2008,88(3):189-191
The experimental data on the shock compression of liquid nitrogen in the megabar pressure range are reported. The experiments have been performed with a spherical measuring setup in which pressure is created by the impact of a steel shell accelerated to a velocity of 23 km/s on the samples. The density of shock-compressed nitrogen at a pressure of about 320 GPa is about 3.4 g/cm3 (compression degree of about 4.2). The experimental data are described using a model equation of state. 相似文献
20.
Batani D Strati F Stabile H Tomasini M Lucchini G Ravasio A Koenig M Benuzzi-Mounaix A Nishimura H Ochi Y Ullschmied J Skala J Kralikova B Pfeifer M Kadlec Ch Mocek T Präg A Hall T Milani P Barborini E Piseri P 《Physical review letters》2004,92(6):065503
We present an experimental point for the carbon equation of state (EOS) at megabar pressures, obtained by laser-driven shock waves. The rear side emissivity of "two-materials two-steps" targets (Al-C) was recorded with space and time resolution and, by applying the impedance mismatch method, allowed a direct determination of relative EOS points. Experiments were performed at the PALS and LULI laboratories using carbon samples with two different values of initial density, in order to explore a wider region of the phase diagram. Previously unreached pressures were obtained. The results are compared with previous experiments and with available theoretical models and seem to show a high compressibility of carbon at megabar pressures. 相似文献